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Old 17th December 2013, 11:34 PM   #631
AVWERK is offline AVWERK  United States
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Location: So Calif.
Don,t give too much on reviews published..
The major high enders wound up who they are because of these reviewers and they do get a chance much more than me or you to try different components and report.
Warts and all, magazines make or break a product.. It's a sad fact all around and positive when one gambles well and wins

Regards
David
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Old 18th December 2013, 06:41 PM   #632
Tom Bloem is offline Tom Bloem  Netherlands
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Well, I was busy but things went wrong, so here is the post.

The image below shows a tonearm without tracking error and offset angle (line A-A'' at the outside of the record will slowly become line B-B''). Nevertheless, it is a straight tonearm without any "mechanics" (only the "pivot" is sliding ~25 mm between the guides A-B).

An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.


Halfway - between the stylus and the “slider” – there is a sphere, drifting in a fluid (to damp all the resonances). The vertical point of rotation is the centre of the sphere; the horizontal point of rotation is the “slider” (the slider sets the azimuth too).
The only force to control the movements of the tonearm is friction (tracking force). Nevertheless, without a second guide (A’-B’) the tonarm will move fast forward. The second guide is not at right angles to the spindle so there is a small force to push the tonearm to the inner side of the record.

The friction of the moving sphere (7 cm diameter) is very low. A weight of 0,01 gram moves the sphere within 6,5 seconds along the line A’-B’ (total weight of the filled sphere is 90 gram). The weight of the tonearm and empty sphere is less, therefore the sphere will be filled with some fluid too.

The length of the armtube from the outside of the sphere to the head shell is minimal. Besides of that, the suspension of the armtube to the sphere will prevent resonances between the second guide and the armtube. The next image shows the construction.

An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.


Because the line A’-B’ is part of an elliptical, it is even possible to replace the second guide (metal bar) by a nylon thread.

The aim of this design is to minimize resonances and unwanted vibrations between stylus and tonearm. Therefore, the first step was to eliminate the offset angle (fixed pivot tonearms). The only way to realize this, is to effectuate zero tracking error.

“Tuning” the tonearm can be done by the use of different viscosities for the fluid in the range M5 - M10.000 (silicone fluid). The goal is to obtain an equal average channel friction. Nevertheless, this is not the best tonearm for an eccentric record collection...

How it “sounds”? I don’t know. I stopped the mounting of the tonearm because I started to design a new type of phono cartridge. The movements of the stylus are detected by electromagnetic waves (it is an optical cartridge and not a MM/MC cartridge). So there have to be some more wiring in the armtube to operate the LED.

I first want to know if I can DIY this cartridge successful before I mount the tonearm. Nevertheless, I have done a lot of experiments to verify the function of this very simple design of a tonearm, so I foresee not much troubles.
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Old 20th December 2013, 07:36 AM   #633
walterwalter is offline walterwalter  Ukraine
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Arm looks as very unusual design. Very interesting. As for the optical cartridge, I've always wondered, why manufacturers completely abandoned that promising design. As well, as Ic (strain gauge), excluding Win Labs, and Soundsmith. At years 197-something Toshiba started both lines, and immediately stopped both.
Attached Images
File Type: jpg Toshiba-SR50-P1.jpg (90.7 KB, 272 views)
File Type: jpg Toshiba-SR50-P2.jpg (106.9 KB, 275 views)
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Old 20th December 2013, 11:46 AM   #634
Tom Bloem is offline Tom Bloem  Netherlands
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@Walterwalter,


It is quite a surprise for me to read there existed already an optical phono cartridge. I could not find the documents (google) so I was unable to expand the drawings of the cartridge. Nevertheless, reading the description I understand that this cartridge is more than only the replacement of the magnet and electromagnetic coils by a light source and photo receivers.


My interest for an optical cartridge is because of the lack of full channel separation of MM/MC cartridges. I didn’t understand the cause very well and therefore I tried to understand the function of the stylus of a vinyl cutter machine (http://phia.home.xs4all.nl/DIY/SC.avi).


My conclusion is that channel separation is – theoretical – 100% because the groove is the result of only 2 linear movements at an angle of 45 degrees. Moreover, when I simulate the movements of the stylus of a cartridge there are no differences (http://phia.home.xs4all.nl/DIY/ST.avi).


The second video shows 2 rectangular apertures. When I fix a LED at one side and a photo receiver at the other side the altering amount of light – electromagnetic waves – that hit the photo receiver will represent the frequencies of the modulated groove.


Yesterday, I received the ordered electronic components and immediately I have done some experiments to verify the function of the passive photo receiver. A single photo receiver – especially a photo diode – acts like an electric generator when it is irradiate by photons (I fastened the photo diode without any other components directly to the probes of the oscilloscope). The output is about 3,5 mV and that is just the value the phono amplifier can handle. Besides of that, the output of a photo diode is highly linear to the input (photons).


Of course, everything is not so easy. Designing a good cartridge is very difficult because of the “microscopic” size of all the parts. Especially the suspension of the cantilever is a very hard job.


About the tonearm: vinyl records are “low tech” in comparison to a CD. When I buy a new record, mostly the hole in the centre is of a bad quality (my old classic music LP’s are far better). No CD will function when the quality of the size (dimensions) is equal to a vinyl record (the laser cannot keep the right track).


I think the tonearm will function properly when the hole of the record is exactly in the centre. Well, that’s not reality for a lot of records. Nevertheless, I expect the tonearm will function without the slider and the 2 guides (so an eccentric record is no problem).


Alas, that will be the start of a new problem: azimuth... The stability of the sphere depends on the existence of the slider. To prevent the sphere from “tumbling upside down” without a slider, there must be a lot of mass at the bottom of the sphere. So the dimension of the sphere will increase far too much (10 cm or more). Experiments showed me that the tracking force will keep the tonearm in a steady position. But what about the moment the platter stops?


It is a challenge to design a simple well damped tonearm. But to suit every imperfection of vinyl recordings is really a big problem...


Now I know for sure the realization of an optical cartridge is not impossible I will mount the tonearm (I first have to make a new head shell and add wiring for the LED. The problem is the influence of the electric current to the wiring of both channels. Shielding all along the trajectory is not easy to realize.)
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Old 20th December 2013, 07:39 PM   #635
walterwalter is offline walterwalter  Ukraine
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Tom Bloem
Here is a short description of Toshiba C100p photo cart (together with drawings).
Stereo Pickups & Phono Cartridges : 1958 - today – Stereotonabnehmer
Manual may be downloaded from vynylengine
Scheme of preamp Toshiba SZ1T in attachment here.

As to record eccentricity I would agree. Nakamichi Absolute Center Search System effectively dealt with that:
https://www.youtube.com/watch?v=SRFpd0ahvj4
Largely underestimated idea, it didn't catch up with audiophiles...
Attached Files
File Type: pdf ve_toshiba_sz-1_schematic.pdf (214.8 KB, 51 views)

Last edited by walterwalter; 20th December 2013 at 08:00 PM.
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Old 21st December 2013, 06:57 PM   #636
Tom Bloem is offline Tom Bloem  Netherlands
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@Walterwalter,

I am very, very pleased with all the links! Especially the first one! I didn’t know the existence of this magazine (Google never showed the link).

The first document shows the function (drawing) of the Toshiba cartridge and I have “walked the same route”. In fact, I am a bit wondering that Toshiba’s cartridge worked so well. I‘ll explain.

This link shows a cantilever in cross-section (scale 100 : 1). In the middle of the carbon cantilever (0,7 x 0,28 mm) you see the modulated groove (real size in relation to the cantilever). Both crossed lines shows the position of the stylus at the moment in relation to the groove. There are not 2 slits – like Toshiba’s cartridge – but a lot of slits to increase both apertures. This is done because the size of electromagnetic waves is enormous in relation to the size of free electrons, moving in a metal conductor (that’s the profit of MM/MC cartridges).

We want the reproduction of all the frequencies between ~40 – 20.000Hz and... we want the right gain (dB) too. So there must be enough physical bandwidth to differentiate all these frequencies. But when these small slits are nearly closed, there is interference between the electromagnetic waves and some frequencies are wiped out (black lines within the spectrum). Therefore I stopped trying to get a direct measurement of the photons of the light source through 2 or more slits.

To obtain a lot of physical bandwidth for all those frequencies we need a magnification of the vibrations of the cantilever (the small rectangle under 45 degrees within the cross-section of the cantilever). In the next drawing the solution: the movements of the cantilever are projected by 2 mirrors to the sensitive surface of a photo diode (the size of the electronic components are in relation to their real properties). The distance from the mirror to the surface of the diode is the magnification.

At the moment, some manufacturers – like Vishay – offer a photo diode in conjunction with an electronic circuit in a small package (a chip, including opamps, resistors, AD converter, etc.). So the output is digital and without a RIAA correction... (I refer to your last link.)

I am aware of the fact that all modern vinyl records are mastered by digital sources. Nevertheless, I think it is a bit strange trying to develop a phono cartridge with a digital output. My intension is to look for a simple solution that can compete with the quality of the engine of high quality MC cartridges. Because 75% of the price of a high-end MC cartridge seems to depend on the coils and the magnet. (I know this is not the truth: I am afraid it is some kind of “audiophile tax”.) So my motivation is just curiosity.

Nakamichi Dragon TX-1000 Turntable… Amazing! I am really impressed by the ingenious solution to centre the record. But the best solution is a hole just in the centre of the record... (I read the turntable cost $7500 in 1982). Because of this video I have looked after the centricity of the last 10 new LP’s I bought recently (all 180 gram “audiophile” jazz records). Only one is perfect centred... Terrible! Oh boy, some people spend a $100.000 for a turntable. Just to play new bad centred records that cause wobble... I am glad the turntable I use at the moment costs about 300 euro (without tonearm and cartridge).

Nevertheless, this “score” is really disappointing. I have to think over the construction of the slider of the tonearm. A wobble of 0,5 mm is no problem, but some of these 10 records have a wobble of 1 – 1,5 mm. That is far too much. A tonearm that can play only a part of all the records without audibly distortion is worthless.
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Old 22nd December 2013, 03:15 PM   #637
walterwalter is offline walterwalter  Ukraine
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Unfortunately, most of both old and new records have eccentricity, so tonearm designers should deal with it...I think, punches on cantiliver (due to eccentricity) with true linear mechanical arms far exceed modest inside force-anti-skating forces of pivot arms. Garrard Zero-100 style approach seems to be least susceptible to side thrusts of all quasi linear ones.
As for Dragon TX-1000, it is remarkable for no-nonsense approach, addressing to real problems, and for $7500 is not as bad, as $100000 turntables dedicated to solving imaginary or secondary ones...
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Old 23rd December 2013, 06:59 AM   #638
Straight Tracker is offline Straight Tracker  United States
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Location: Prescott, Arizona
Default Hello berlinta

Quote:
Originally Posted by berlinta View Post
I hope to be seeing Ralf's (Straight Tracker) newest Linear tracking arm version here soon.

Merry Christmas Ralf! And the same to all other DIYers here :-)

Frank
I would have shown my "newest Linear tracking arm version" some time ago if it wasn't for the fact that it incorporates two patentable features, one of which can be used in tone arms of other designs. I have been listening to my new tone arm for most of 2013, going through my entire LP collection and having a grand old time. I am taking the tone arm to the 2014 CES to see if I can interest someone to manufacture it and take care of the patent too. I now call it a "pivoting, sliding, straightline tracking tone arm". And yes, even though it uses a servo with its inherent "servo error", it has absolutely no tracking error!

I am also working on my newer 2014 model which operates on the same principle but gets away with a track length that is one half the length of my present arm.

If you'll be at the 2014 CES, I'll show it to you.

And a merry Christmas to you and your family too.

Sincerely,

Ralf
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Old 23rd December 2013, 07:22 AM   #639
Straight Tracker is offline Straight Tracker  United States
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Default Hello berlinta

Quote:
Originally Posted by berlinta View Post
So: move the sled/platform at an average speed based to the groove pitch, superimposed by the non-linear arm angle - sled position function, do that without exiting arm resonances or disturbing the cart(the real challenge) and: Voila! A near perfect arm.
I did some number crunching concerning the above idea. I was going to place four Hall Effect sensors along the track, each one changing the step rate to the stepping motor as the carriage rolls by. That would have worked perfectly until I looked at "also, sprach Zarathustra" on the Deutsche Grammophone label and noticed 1.9 inches (48.26mm) of unrecorded run out groove. At a pitch of .25 inches (6.35mm) there is no way for the tone arm's carriage to keep up without the use of a servo.
However, I know people who are smarter than I am.

Sincerely,

Ralf
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Old 23rd December 2013, 02:24 PM   #640
Tom Bloem is offline Tom Bloem  Netherlands
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@Walterwalter,

I have looked after my old records to check the centricity. Nearly all the records (classic music) are centric. When I bought these records about 35 years ago they cost some 30% more than “normal” LP’s (popular music). Some labels: Argo, Archive, BASF, Jecklin, Philips, RCA, Telefunken, etc. I have a couple of old Russian and Polish LP’s too: nearly all are centric.

Your link to the video of the Nakamichi Dragon TX-1000 turntable shows the way to master the centricity of vinyl records: measuring the inner groove. In this way it is possible to get the point of centricity (by light or mechanical). Because eccentricity and warps are the most dominant negative influences on the quality of the lower part of the frequency spectrum of the phono cartridge it is very important for “audiophiles” to get centric records.

Because those high quality vinyl labels exist no more, new vinyl records are mostly too eccentric (my personal experience). Nevertheless, it is very important to develop a workable solution for this problem. Conclusion: the guy who designs a handy tool to mill a new centric (oversized) hole in vinyl records will attribute more progress to the quality of vinyl recordings than the inventor of the “ultimate tangential tonearm”. I am not the guy who loves money, therefore trying to find a DIY solution is more attractive for me. I will think it over.
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